1. Field of the Invention
The present invention relates to a non-volatile memory device and a fabrication method. More specifically, the present invention relates to a non-volatile memory device formed on a glass substrate, and a method for fabricating a non-volatile memory device.
2. Description of the Related Art
Generally, a non-volatile memory device may be classified into a floating-gate memory device and a charge-trapping memory device. The floating-gate memory device is a device for maintaining a memory by using a potential well. The charge-trapping memory device is a device for maintaining a memory by trapping charges in a trap region inside a nitride film or a trap region present in an interface between a nitride film and an insulator.
A representative form of the charge-trapping memory device is a Silicon-Oxide-Nitride-Oxide-Silicon (SONOS) configuration. Typically, the SONOS configuration may include a sequential stack of a semiconductor substrate, an ONO configuration, and a gate electrode. The ONO configuration may include a sequential stack of a tunneling oxide film, a nitride film and a blocking oxide film. The tunneling oxide film may tunnel electrons into a trap region inside the nitride film or a trap region of an interface of the nitride film. The blocking oxide film may block charges from moving between the nitride film and the gate electrode. The trap region may store charges. Source/drain regions may be provided in the semiconductor substrate on either side of this stack.
Recently, creation of a non-volatile memory device on a glass substrate has been investigated. Such a configuration may include a sequential stack of the glass substrate, the ONO configuration, and the gate electrode. The glass substrate may include a protective layer, e.g., a buffer oxide film, thereon to protect the glass substrate. A polysilicon layer may be provided on the protective layer. Source/drain regions may be provided in the polysilicon layer on either side of this stack.
Creation of the polysilicon layer may include crystallizing an amorphous polysilicon layer, e.g., by irradiating the amorphous polysilicon layer with a laser. Thus, surfaces of the polysilicon layers may be rough and non-uniform, which may result in a large leakage current being generated. In other words, a leakage current may be significantly increased due to the non-uniformity and roughness of the surfaces of the polysilicon layer. Therefore, such a non-volatile memory may function abnormally during programming/erasing operations.